The fifth issue concerns the reason for the law of jihad in Islam. Some believe that there should be no jihad in religion at all; that religion should contain no law of war: that since war is bad in itself, religion must oppose it and not itself establish war as a law.
On the other hand, we know that jihad is a basic principle in Islam. When we are asked how many are the subsidiary beliefs of Islam (furu’ ad-Din) we say, “Ten – prayer, fasting, khums, zakat, hajj, jihad, etc.”
Of the arguments that Christians propagate in an extraordinary fashion against Islam is this one. First, they ask why such a law exists in Islam and then they state that due to this legal permission, Muslims started wars with various peoples, forcibly imposing Islam on them. They claim that the Islamic jihads were all fought for the imposition of Islamic beliefs. It is due to this permission that Muslims imposed Islam by force, which is how, they say, up to now, Islam has always spread (“by the sword”). They say that the principle of jihad in Islam and one of the basic rights of man, viz. freedom of belief, are in eternal conflict. This is one of the issues to be discussed.
A second issue is the difference that Islam has maintained in the laws of jihad between the mushrikin – the polytheists – and the non-polytheists. There is a provision for living in harmony with the People of the Book that is not applicable to the polytheists.
Another issue is the question of whether Islam differentiates between the Arabian peninsula and the rest of the world. Has Islam appointed for itself a place as its headquarters, its center, wherein no one from amongst the mushrikin or the People of the Book is admitted? And is that place the Arabian peninsula, while in other places Islam is not so severe, and, for example, lives in harmony with the mushrikin or the People of the Book? In short, is the Arabian peninsula any different in these terms or not?
The answer is that between Mecca and other places, there is undoubtedly a difference. In the verse preceding the one under discussion we are told:
﴾O ye who believe! Truly the Pagans are unclean; so let them not, after this year of theirs, approach the Sacred Mosque. (9:28)﴿
The fourth issue concerns agreements with mushrikin. Is a Muslim allowed to make agreements with such people? Can he make promises to them? And if he does, is the promise or agreement to be honored or not?
The last issue concerns the conditions of war. When Islam has legalized warfare, what kind of warfare, in terms of the particular conditions of war, does Islam see as legal, and what kind of war does it see as forbidden? For example, does Islam consider the killing of a whole people to be lawful or forbidden? Does Islam view as permissible the killing of those who have not lifted the sword: old women, children, men who are peacefully engaged in their jobs and trades? Is the killing of all these in the view of Islam permissible or forbidden? These are all issues that have to be discussed. The verses pertaining to jihad occur in many places in the Qur’an. We shall try to compile all of them with the help of God so as to obtain the view of Islam on this matter.
source: english.almaaref